The invention is directed to a process for the production of solid particles from liquid bioinjurious waste, e.g., radioactive concentrates, which can serve for storage or as intermediate product for storable particles.
There are already known a number of processes by which liquid waste concentrates can be converted into a storable form. Most processes start by separating off the non-toxic liquid, e.g., water and supplying the solids remaining behind either with or without a further treatment to storage.
The simplest of these processes consists of evaporating the concentrate in a container to dryness whereupon the container with the solids is closed and is supplied to a storehouse. This drying in a container is described in German Pat. Nos. 1,564,276 and 1,614,071. The disadvantage of this process is that as a rule the solids are corrosive and frequently are even hygroscopic salts so that there occures a corrosion of the container after a shorter or longer time which can only be partially avoided by the use of stainless steel containers. This solution is expensive and dry bioinjurious waste obtained in this manner is present partialy in finely divided structure so that in further handling or storage of the waste there can be caused partially a contamination, e.g., by leaching out or otherwise burdening the environment.
Furthermore, there are also known processes in which the water is tied up in the tank or container. To these below the known cementation process as well as the bitumenization after adsorption on solid materials (Hanss, German Os No. 2,421,142). The disadvantages of such processes correspond to those previously described. Additionally, at higher active waste content there occurs increased radiolysis of the tied up water whereby combustible or explosive gases are formed.
Furthermore, it is known to dry concentrates of bioinjurious (i.e., biotoxic) waste in a so-called thin layer evaporator whereby likewise pourable solid residues are sought. The solids deposit in the inside of the thin layer evaporator so that a proper apparatus for shearing off the solids is required. These solids, however, are of different natures and adhere partially so strongly to the inner surfaces that the strength of the wiper blades, scraper or the like frequently is not sufficient and these are damaged. This type of damage to the apparatus can only be eliminated by considering particular precautionary measures since the solid residues can exert an injurious effect on the service personnel. In Dollgast German Pat. No. 1,764,586, furthermore, there is described the employment of roller dryers for treatment of concentrates injurious to the environment. To the advantage of the reduced final volume, however, there is the disadvantage of the ability to leach out as well as likewise occurring waste air problems.
It is also known to employ bitumenization screws for the treatment of environmentally injurious concentrates, e.g., see Meier German OS No. 2,361,732. The advantages of the continuous process and the utilization of the volume are opposed by the extraordinarily disadvantageous accumulation of oily and contaminating liquids being evaporated.
A further process for the treatment of radioactive concentrate containing liquid waste materials is described in German Pat. No. 2,012,785. In this process there is added bone glue or a similarly acting binder to the radioactive concentrate and it is converted by spray drying into solid residues or granulates. For spray drying there is used hot air or another suitable gas which after the drying is freed from dust and with cooling freed from water in order to then in a closed cycle to again be heated up and be fed to the spray drying. In this process there result consequently two different groups of solid residues. On the one hand, those which accumulate in the space in which the spray drying is carried out and on the other hand those which are obtained in the subsequent removal of dust from the gases. The solid residues obtained in the removal of dust are powdery and very finely divided so that they dust very easily and thereby can again cause a load on the environment.